Continuous ambulatory monitoring of physiological parameters can expand our understanding of the basis of clinically-relevant symptoms of daily life and how their experience is shaped by a subject's concurrent activities and behaviors. Although promising new, technologies have been developed, ambulatory monitoring data are often difficult to interpret. A major problem is that physical activity is not controlled as it is in the laboratory or clinic; if unknown, it can lead to a confusion of ordinary exercise-induced physiological changes with disease indications. Thus, a clinically-relevant ambulatory monitoring system advantageously should register motor activity to provide an evaluative context that can enable a clinician to judge whether any abnormal value (e.g., in the ECG or respiratory pattern) can be attributed to physical exercise or represent physiological dysregulation. A diary, either paper-and-pencil or electronic in which monitored subjects may record their activity, posture, and location, can help with further clinical interpretation by providing more contextual information. However, diaries are unsatisfactory when used alone because of often documented inaccuracy in reporting changes in location and activity levels.
Speech is an important activity that can confound ambulatory monitoring, especially of respiration. Speaking episodes, one of the most frequent types of physical activity and behavior, can alter a variety of physiological systems in addition to pulmonary functioning. For example, heart rate typically increases with conversational speaking from 5 to 10 beats per min. Heart rate increases can be much higher in socially demanding situations. Auditory recording with a microphone has been used to quantify speech activity, but is limited because it also picks up sounds other than the voice of the person monitored, like ambient sounds and the speech of others. A throat microphone is more selective, but wearing it over extended periods is inconvenient and attracts undesirable social attention to the monitored subject.
Inductive plethysmography (IP) is a scientifically and clinically accepted gold standard for unobtrusive respiratory monitoring of cardio-respiratory function, and has been used widely in clinical and research settings. For respiration, this technique approximates the amount of air moved by the respiratory system by measuring the expansion and contraction of both the rib cage and abdominal compartments, using IP sensors consisting of sinusoidal arrangements of electrical wires embedded in elastic bands. A high frequency, low voltage oscillating current is passed through the wires to generate a magnetic field needed to measure the self-inductance of the coils, which is proportional to the cross-sectional area surrounded by the band. After calibration of the rib cage and abdominal bands, a weighted sum of the two signals corresponds or is proportional to tidal volume.
Thus there is a need in the art for improved systems and methods for registering or detecting physical activity, especially speech, and for utilizing activity information to provide improved and more reliable interpretation of ambulatory monitoring data. Such systems should be directly applicable to ambulatory monitoring by inductive plethysmography.
Citation or identification of any reference in this section or any section of this application shall not be construed that such reference is available as prior art to the present invention.